Process control relates to the control of processes, e.g., manufacturing processes, through the use of control devices including sensors, e.g., temperature sensors, pressure sensors, flow sensors, and digital computers. Presently, many sensors and other types of control devices include a central processing unit, memory for a program, e.g., function routines, parameters and control variables. Control devices which include CPUs are often referred to as smart devices.
Smart devices are often programmed to perform a variety of functions, e.g., convert pressure into a value representing volume or convert a command into a signal used to move a valve. Functions are frequently performed by software as well as hardware. A function, whether implemented in hardware or software, can be characterized as a function block. Each function block of a device may have a plurality of inputs and outputs, as well as internal parameters and internal signals which are used to perform the function.
A control system may include a plurality of smart devices coupled together via, e.g., a digital bus operating according to a preselected communication protocol. A Fieldbus is a bus which operates according to the Fieldbus communication protocol which is a bidirectional digital communications protocol. A Fieldbus network is a plurality of smart devices coupled together via a Fieldbus.
The Fieldbus communications protocol is described in "SMAR, FIELDBUS TUTORIAL", which is published by SMAR INT'L CORP., 1993 which is hereby expressly incorporated by reference. As discussed in the cited reference, the Fieldbus communications protocol permits devices coupled to a Fieldbus to communicate system configuration information, sensed values, function parameters, etc. between each other and a master computer over a Fieldbus.
Access to the Fieldbus may be controlled using a token system, wherein a token is used to indicate which device is authorized to initiate a transaction on the Fieldbus. In such an embodiment, a master device or computer, sometimes referred to as a link active scheduler, serves to insure that the token is passed to each device requesting to initiate a bus transaction according to a preselected scheduling order.
In addition to the "SMAR, FIELDBUS TUTORIAL" additional references which describe the Fieldbus communications protocol include FIELDBUS FOUNDATION.TM., Fieldbus Specification, Function Block Application Process, Parts 1 and 2, Revision PS 1.0, Apr. 27, 1995 which are hereby expressly incorporated by reference. The cited Fieldbus Specification documents, are useful in providing insights into the communication protocols used for communicating information between various function blocks implemented in devices coupled to Fieldbus networks and for providing a better understanding of function blocks in general.
While Fieldbus systems offer several advantages over prior art control networks, because a plurality of different smart devices may be coupled to a single Fieldbus, and each device must often be configured with, e.g., control and parameter information so that it will properly respond to other devices on the bus and perform the various functions desired, it has become a relatively complicated process to program field mounted devices coupled to a Fieldbus.
The difficulty in configuring Fieldbus devices and a Fieldbus network is often complicated by the limited screen size provided on field mounted devices and the limited number of inputs provided on such devices. With a relatively limited number of inputs on a device, e.g., one or two buttons, it is often necessary to scroll through a plurality of menus, in a preselected sequence, until the device is properly set. Errors in setting parameter values may require an operator to scroll through several screen displays before the parameter values can be reset.
In addition, it may be difficult or impossible to configure the entire network using the inputs and display incorporated into a single field mounted device requiring an operator to individually configure a plurality of field mounted devices by physically visiting and setting each device.
Accordingly, there is a need for an improved method and apparatus for configuring a Fieldbus network so that an operator can configure the entire network with a minimal amount of difficulty. Furthermore, it is desirable that the operator be able to visually see a graphical representation of the Fieldbus network including the devices coupled thereto when configuring the network. It is also desirable that the operator be able to easily set and reset parameter and control information fox each of the system devices from a single location.
It is also desirable that the configuration method and apparatus be capable of being used from any point on the Fieldbus, e.g., either in a control room or in the field near a device on the Fieldbus.